"I will not give up. [Commission President Jose Manuel Barroso] will put this on the Commission agenda again before the end of November."

On Monday, the European Parliament criticised the lack of female candidates for the European Central Bank (ECB).

A parliamentary committee - in a resolution passed by 21 votes to 12, with 13 absentions - called on the European Council to withdraw the candidacy of Luxembourg's Yves Mersch for the ECB executive board, saying his appointment would mean that the board would be all male up until 2018.

'Time is now'

The debate on Ms Reding's plan was due in Strasbourg on Tuesday, which could have led to a vote in the European Parliament to make gender quotas mandatory across the 27 countries in the European Union.

But lawyers told the Commission that the 40% quota plan, including hefty sanctions on companies in EU countries that did not meet the target, could not be enforced under EU treaties.

Earlier reports had suggested the directive was being diluted, before a decision was made to postpone it.

At the moment, less than 15% of board positions in EU member states are currently held by women, according to the Commission.

Ms Reding's proposals on compulsory numbers of women come after France, Spain, Italy, Iceland and Belgium introduced quota laws. Norway, which is not an EU member, has had a 40% quota since 2003.

Her opponents argue that voluntary targets and increased efforts to change attitudes would be more effective in the long run.

UK Business Secretary Vince Cable is leading a campaign against the quota proposals, backed by ministers from eight other countries.

In the UK, the percentage of women on the boards of FTSE 100 companies has risen over the past year to a record 16%, but the UK government wants the biggest listed companies to have a minimum 25% of female directors by 2015.